1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Copied from the kernel sources to tools/:
4 *
5 * Memory barrier definitions. This is based on information published
6 * in the Processor Abstraction Layer and the System Abstraction Layer
7 * manual.
8 *
9 * Copyright (C) 1998-2003 Hewlett-Packard Co
10 * David Mosberger-Tang <davidm@hpl.hp.com>
11 * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com>
12 * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
13 */
14 #ifndef _TOOLS_LINUX_ASM_IA64_BARRIER_H
15 #define _TOOLS_LINUX_ASM_IA64_BARRIER_H
16
17 #include <linux/compiler.h>
18
19 /*
20 * Macros to force memory ordering. In these descriptions, "previous"
21 * and "subsequent" refer to program order; "visible" means that all
22 * architecturally visible effects of a memory access have occurred
23 * (at a minimum, this means the memory has been read or written).
24 *
25 * wmb(): Guarantees that all preceding stores to memory-
26 * like regions are visible before any subsequent
27 * stores and that all following stores will be
28 * visible only after all previous stores.
29 * rmb(): Like wmb(), but for reads.
30 * mb(): wmb()/rmb() combo, i.e., all previous memory
31 * accesses are visible before all subsequent
32 * accesses and vice versa. This is also known as
33 * a "fence."
34 *
35 * Note: "mb()" and its variants cannot be used as a fence to order
36 * accesses to memory mapped I/O registers. For that, mf.a needs to
37 * be used. However, we don't want to always use mf.a because (a)
38 * it's (presumably) much slower than mf and (b) mf.a is supported for
39 * sequential memory pages only.
40 */
41
42 /* XXX From arch/ia64/include/uapi/asm/gcc_intrin.h */
43 #define ia64_mf() asm volatile ("mf" ::: "memory")
44
45 #define mb() ia64_mf()
46 #define rmb() mb()
47 #define wmb() mb()
48
49 #define smp_store_release(p, v) \
50 do { \
51 barrier(); \
52 WRITE_ONCE(*p, v); \
53 } while (0)
54
55 #define smp_load_acquire(p) \
56 ({ \
57 typeof(*p) ___p1 = READ_ONCE(*p); \
58 barrier(); \
59 ___p1; \
60 })
61
62 #endif /* _TOOLS_LINUX_ASM_IA64_BARRIER_H */